Can someone help me fix some of the issues with my game

heres a list of the things id like to fix

  1. bullet lag/weirdness if you hold down the fire button aka space the bullets will fire however after some time the bullets will start to go the wrong direction and eventually you will end up with the bullets no longer appearing and im not quite sure how to fix this
  2. movement differential the if one person is running a better computer and so the have a better frame rate they will in turn go faster than others and if u have a bad pc then u go really slow and cant do anything and im not really sure how to fix this one
    3.any suggestions on what to add

the project is at!/wings-of-fire
the scripts are as follows
game.js the game script does mostly the stuff for displaying everything and runnning the game loop
map.js the script where the map displaying functions are written
plane.js same as map exept plane
join.js the scripts for when u first log in and first open the page
login.js self explanitory
oops.js a set of functions that act sorta like pjs for canvas only using these because i thought they wourld be simpler but i guess it was a bad idea

anyone gonna help?? i would really like to finish this one and cant figure out why its not working properly

For bullet lag, you can either have the server tell the client where the bullets go based on their heading a few ms ago, or the client tell the server where it thinks the bullets go